This paper presents VisGuides, a discussion platform to facilitate the collection, evaluation, critique, revision, and dissemination of visualization guidelines. As visualization becomes a more widespread discipline with much more attention by designers and the general public, we need to ensure mechanisms for communicating, transferring, and accessing visualization knowledge. A visualization guideline can be anything ranging from good practices, empirical studies, and survey reports with the goal to inform visualization design and understanding. Thus, our forum aims (i) to collect visualization guidelines, (ii) to discuss guidelines and collect respective empirical references, and in the long run, (iii) to establish formal knowledge about guidelines by analyzing the forum content and the consensus of discussions. This paper describes the VisGuides forum and outlines our preliminary research towards shedding more light on visualization guidelines. VisGuides is accessible online at visguides.org.